Simulation of VBF process with polarized vector bosons

> Does that mean that I directly collide the two vector bosons?

Yes that's correct.

Olivier

> On 30 Jun 2023, at 15:05, Anna Tegetmeier <email address hidden> wrote:
>
> New question #707163 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/707163
>
> Dear Madgraph experts,
>
> I want to simulate a vector boson fusion (VBF) process, where the two vector bosons that fuse are polarized and then give a Higgs pair (e. g. WL WL -> H H).
> So far I used the syntax
>
> generate w+{0} w-{0} > h h QED=2 QCD=0
>
> and set the following parameters in the run card:
> 0 = lpp1
> 0 = lpp2
> none = pdlabel
> none = systematics_program
>
> In the description it says that lpp=0 corresponds to no pdf. Does that mean that I directly collide the two vector bosons? If not is there another possibility to simulate the process that I described (I know there is the possibility to use the eva approximations with electron and muon beams, but since my general interest is in VBF I do not want to have an electron and muon beam)?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks Olivier Mattelaer, that solved my question.

Hi Olivier,

I have a follow-up question to this. If I try to shower this process with phythia 8.308 I get the following error:

PYTHIA Error in Pythia::init: cannot handle this beam combination
PYTHIA Abort from Pythia::init: checkBeams initialization failed

Does that mean it is not possible to shower this kind of process?

Best,
Anna

Hi,

I'm not a pythia8 expert/author so I'm not an autority to answer your question.
But without PDF for the initial state, you will not be able to do ISR for sure.
So you need at minima to remove ISR.
Also you need to enforce weak shower for this process since you do not have any QCD radiation.
Obviously even if you suceed to make it trough, this will not look like a VBF process.

Cheers,

Olivier